Cybertron

Cybertron was the former home world of a sentient robotic race known as the Cybertronians. The planet was ravaged by the Autobot-Decepticon Civil War.

History
For millions of years, the Cybertronians lived peacefully on Cybertron. However at some point, a faction of Cybertronians known as the Decepticons arose and sought to rule Cybertron with an iron fist. Many resisted this ideology and formed a resistance movement called the Autobots, led by Optimus Prime, to fight for freedom.

These two factions ultimately clashed together for the future of their planet, resulting in massive infighting that caused a millennia-long civil war, with casualties on both sides. As the war progressed, the planet was ravaged and the Autobots were being further pushed back by the Decepticons, with several of them fleeing Cybertron to find refuge. Therefore, Optimus ordered many of his lieutenants to flee Cybertron and tasked one his lieutenants, B-127, protect a planet called Earth and establish a base for the Autobots there. As most of the remaining Autobots departed, Optimus remained behind to fight off the Decepticons.